Video endoscopes and laparoscopes have been in general use since the 1980s. Laparoscopes are rigid devices that may be used in minimally invasive diagnostic and surgical procedures. In contrast, endoscopes are flexible devices that may be used in invasive diagnostic and surgical procedures. While the implementation of an endoscope and a laparoscope are different from one another, endoscopy and laparoscopy systems are both arranged to capture optical signals and generate a video image.
A typical laparoscopy system includes a hand-tool and a console with a video display. The body of the hand-tool includes a long rigid tube with a digital camera that is mounted proximal to an end of the tube. A series of rod lenses form an array that extends from an end of the tube to the digital camera so that a video image can be collected when the tube is extended into a body cavity of a patient. The digital camera communicates the collected video image to the console through a series of wires that also extend through the tube such that the video image can be viewed on the video display. Also typically, a light source is mounted on the console that is based on a xenon lamp. Light from the light source is coupled to the laparoscope tube through a fiber optic coupling. Optical fibers extend though the length of the laparoscope tube to a distal end where a concentric ring, or partial arc is formed to provide an appropriate illumination for the video image. The illumination power can be adjusted at the console to provide an image with an appropriate brightness level for the video display.
A typical endoscopy system also includes a hand-tool and a console with a video display. The body of the hand-tool includes a hand piece that is connected to a long flexible tube with a digital camera that is mounted at a distal end of the tube. The digital camera is arranged to capture light, convert the captured light into an electronic signal, and send the electronic signal through the flexible tube to the hand piece. The hand piece is arranged to send the electronic image to the console, where the image can be viewed on the digital display. The light source for the endoscope is also mounted on the console and based on a xenon lamp, with light being coupled to the endoscope tube through a fiber optic coupling. Optical fibers extend though the length of the laparoscope tube to a distal end, where the optical fibers terminate as apertures that are located about the camera lens.
Endoscopes and laparoscopes can be end-looking or side-looking. End-looking devices have a field-of-view that is positioned directly in front of the end of the device. Side-looking devices can have their field-of-view located at 70°, or some other angle that is off-axis from the end of the tube. The field-of-view varies according to the particular application. For example, a colonoscope often has a 140° diagonal field-of-view, while a laparoscope may have a field-of-view that is closer to 70° diagonal.
The basis of the digital camera devices in both endoscopy and laparoscopy systems is typically a solid-state focal plane sensor array such as a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) device. The pixelated, focal plane sensor array consists of an array of light-sensitive elements that develop an electrical charge when exposed to light from a conjugate point in the field-of-view. An electrical charge is accumulated by a light-sensitive element over a selected sampling interval that corresponds to a shutter or exposure time. The accumulated electrical charge for the light-sensitive element is indicative of the brightness level for the corresponding conjugate point from the field of view for the selected sampling interval. The accumulated electrical charge associated with the light-sensitive element can be amplified, transmitted, processed, displayed, and recorded.
Typically, a light-sensitive element contributes to a unit or pixel of the total image. The resolution or clarity of the image depends upon the total number of pixels or light receptors that are in the sensor array. Standard cameras used for laparoscopy or endoscopy contain between 250,000 and 380,000 pixels. The clarity of the image that is eventually displayed or recorded depends upon both the sensor array resolution and the resolution capability of the monitor, as well as another resolution that is associated with a recording medium. Standard consumer-grade video monitors have 350 lines of horizontal resolution, while monitors that are preferred for surgical applications have about 700 lines of resolution.
Endoscopes often include irrigation channels and working channels for instruments, in addition to a steering apparatus that can be used to aim and push or pull the tip of the endoscope toward a targeted area in the patient under the direction of a clinician. Instruments such as forceps, scissors, needle drivers, and other devices have been developed to pass through the working channel of the endoscope for use by a clinician for a variety of uses such as taking tissue samples, delivering medicine, etc. In contrast, laparoscopes typically do not typically include working channels and necessary instruments are typically introduced to the procedure through a separate small incision in the patient. Laparoscopes include facility to pass certain very small instruments such as trocars or rings that line the incisions to prevent undue binding or damage as well as maintain a seal.
During a diagnostic or surgical procedure, a clinician guides the endoscope or laparoscope into the desired region of the patient while viewing the video image from the device on the video display. When the endoscope or laparoscope is positioned in or pulled through the appropriate region, the surgeon or clinician may perform a procedure using instruments that may be necessary as previously discussed.
Whereas in many cases older technology boroscopes or fiberscopes would automatically maintain a known orientation when the scope was rotated (the proximal viewing end being rotated along with the distal end), clinicians may tend to lose the reference horizon when rotating a video scope. Video-based scopes have heretofore typically output an image to a (non-rotating) video monitor that is constant relative to the x-y coordinates of a (rotatable) image capture mechanism. Thus, “up” on the video monitor does not necessarily always represent “up” relative to the clinician's reference plane. To combat this effect, clinicians must typically pay close attention to exploratory movements of the tip or instruments in the field of view.